以单四拍的方式用LPC2138与L297、L298控制步进电机,上电时步进电机按初始化的速度转动,按下4个按键分别执行增、减速；正、反转，同时上位机显示控制指令。-In single step mode using LPC2138 and L297, L298 stepper motor control, power step motor according to initialize the rotation speed, press 4 keys are implemented by, de